Known airline lubricators typically have a primary air flow passage through which air passes from an inlet port to an outlet port. The primary air flow or a portion of the incoming air flow is directed past an eductor orifice from which lubricant is dispensed as a spray into the air flow for mixing therewith by reason of the lower pressure of the moving air relative to the pressure in a lubricant bowl from which the lubricant is drawn. For proper operation, primary air flow heretofore has been restricted by an elastomeric flapper which extends across and normally closes the main air flow passage but is deflectable by pressure of air in the primary air flow passage upstream of the flapper.
In some lubricators, the primary air flow follows a relatively tortuous path involving multiple turns. Higher flow capacities may be achieved if primary air flow passes straight through the lubricator. However, lubricators using a straight flow path have encountered poor service life of the elastomeric flapper which then is exposed to high impact forces in use. In lubricators having a more tortuous air flow path, air momentum is absorbed as it traverses a turn, and this reduces the impact force on the elastomeric flapper located downstream of one or more turns, thereby improving the service life of the elastomeric flapper. It would be advantageous to be able to increase the flow capacity of a lubricator without a corresponding reduction in the service life of the elastomeric flapper, or vice versa.
Another desirable objective would be to reduce the cost and complexity of producing and servicing the lubricator. For low cost production, typically a major portion of the head of the lubricator is formed by a die casted body which has various machining operations performed thereon. In many if not most of the presently commercially available lubricators, a common design feature is an angled passageway drilled in the body to form a connecting passageway either supplying lubricant to a sight tube (often in the form of a dome) or supplying lubricant from the sight tube to an internal device which dispenses the lubricant into the air stream passing through the lubricator. It would be advantageous to provide a lubricator that does not require drilling of the angled passageway in the body the to reduce the amount of required machining, while at the same time simplifying assembly of the lubricator.
Some lubricator designs have previously avoided the need to drill the angled passageway. One such design limited the extent to which the sight tube could be transversely offset from the internal device. Another such design involved the use of a relatively difficult to install tube seal and did not employ a secondary air flow path for directing and accelerating air flow past the eductor orifice. Instead, a plastic insert had formed therein a transversely extending passageway leading directly from a location centered beneath the sight tube to an eductor orifice opening directly to the main flow passage of the lubricator.